Tiger-Striped PASH: Recognition of a Unique Morphology Allows for a Zippered-Up Diagnosis of Pseudoangiomatous Stromal Hyperplasia of Breast

Pseudoangiomatous stromal hyperplasia (PASH) of the breast is histologically characterized by anastomosing and slit-like spaces invested by collagenous stroma and lined by flattened, spindle cells. These clear spaces that may mimic microscopic vascular channels do not contain red blood cells. Immunohistochemistry (IHC) studies may also help to confirm a diagnosis of PASH, with the spindled cells marking positively with CD34 and PR while demonstrating no reactivity with more specific endothelial antigens such as CD31 and ERG. In the current case, a 39-year-old female was diagnosed with cellular PASH of the right breast with unique histological patterns showing “tiger-striped” and “zippered” histologies. To our knowledge, this is the first report of these unique variant PASH morphologies.

Mechanical Causation of Biological Structure: Productive Pulls Produce Persistent Filaments in a Human Fibroblast Model of Matrix Development

During development, mesenchymal cells direct the elaboration of extracellular matrix that shapes the initial animal bauplan which subsequently grows to produce mechanically-competent structure. To gain insight into the processes that initiate matrix formation at the cellular level, high temporal and spatial resolution videos were obtained from a primary human corneal fibroblast (PHCF) cell culture system known to produce an organized, collagenous stroma similar to a human cornea. The images were taken over a 4-day period prior to culture confluency which permitted a clear view of the cell kinematics and any elaborated filaments. The movies reveal an active cellular system in which the PHCFs execute five types of high-velocity and high extensional strain-rate 'pulls' that produce persistent filaments. In four of the pull types, average maximum strain rates (~0.1-0.33s-1) were adequate to induce aggregation and/or crystallization in crowded biopolymer systems. The results demonstrate that PHCFs have the capacity to mechanically induce the formation of biopolymer structures intercellularly and in the path of force.

A Case Report of RRBP1-ALK Fusion Gene-Positive Epithelioid Inflammatory Myofibroblastic Sarcoma With Collagenous Stroma

Background: Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is a rare variant of inflammatory myofibroblastic tumors with distinct morphological features and malignant clinical behavior. ALK is positive in all EIMS cases, the RANBP2-ALK fusion gene has been detected in most EIMSs, but several RRBP1-ALK and EML4-ALK fusion genes have also recently been reported.Case presentation: Here, we report a case of RRBP1-ALK fusion-positive EIMS in the colon. The patient was a 26-year-old man. A pelvic mass was found in a routine physical examination and was completely resected. Microscopically, the tumor cells were rounded and epithelioid in shape. Diffuse collagenous stroma and focal inflammatory infiltration were present. ALK was positive, with a pattern of cytoplasmic staining with perinuclear accentuation, and the RRBP1-ALK fusion gene was detected by targeted next generation sequencing. The patient began to take crizotinib from October 2019 to July 2020, and the patient is presently in good condition. No synchronous or metachronous metastases was found.Conclusions: EIMSs with different ALK fusion partner genes have unique staining patterns, which may provide clues for diagnosing EIMS. EIMS cases with RRBP1-ALK fusion gene and with diffuse collagenous stroma may have a good prognosis.

Chondroid Syringoma Involving the Sub-brow Area

Purpose: Chondroid syringoma of the skin is a rare subcutaneous tumor and localization in the eyelid and orbital region that has rarely been described. We report a case of chondroid syringoma that involved the sub-brow region and was accompanied by hair loss. Case summary: A 57-year-old women presented with a mass on the lateral side of the left sub-brow region which was observed 25 years earlier. The mass, which recurred 2 months after surgery at another hospital through a skin incision was accompanied by an itching sensation. The mass was not tender or ulcerated but was reddish with superficial blood vessels and had a smooth surface with hair loss at the site of the mass. The mass showed high signal intensity on a T2-weighted magnetic resonance image and a round echogenic nodule with an irregular hypoechoic portion was observed on ultrasonography. A full-thickness excision including the adjacent normal tissue of the sub-brow mass and direct closure were subsequently performed. The pathological diagnosis was chondroid syringoma which was revealed as numerous tubular structures with various lumens in a collagenous stroma. Mucinous and fibrous findings were also observed. No recurrence was detected during the first 2 years after surgery. Conclusions: Chondroid syringoma in the eyelid and sub-brow region is uncommon. Complete resection is required to differentiate it from a malignancy and reduce the possibility of recurrence. Incomplete resection or capsular rupture during removal of the tumor could induce recurrence or a malignant change in the tumor.

Solitary Fibrous Tumor of the External Auditory Canal

Solitary fibrous tumors (SFTs) originating from the external auditory canal are uncommon; only few cases have been reported in the literature. In this article, we report a case of a 35-year-old man who presented with a 6-month history of a gradual swelling in the entrance of the left external auditory meatus associated with hearing loss. The tumor was surgically removed, and histological examination showed spindle-cell proliferation with a collagenous stroma. Immunohistochemically, the tumor cells were positive for CD34 confirming the diagnosis of an SFT. Although SFTs are benign, complications such as relapses and metastasis after excision were reported. Thus, a careful and long follow-up is recommended.

Giant Spindle Cell Lipoma of Middle Finger: Case Report and Review of Literature

We present a case of a giant Spindle cell lipoma of dimensions 11 cm × 7 cm, involving the middle finger of a 62-year-old female, without distal neurovascular deficits. Spindle cell lipoma is a rare subtype that accounts for 1.5% of all lipomatous tumors. They show a heterogeneous mixture of lipomatous tissue with mature adipocytes interspersed with spindle-shaped cells, without atypia in a sclerotic collagenous stroma. Immunohistochemical (IHC) marker CD34 was positive but negative for S100. The entire tumor was removed with recovery of full range of movements. The case is reported due to the unusual location of a rare variant of giant lipoma involving a finger.

Development and Pathology of the Equine Mammary Gland

An understanding of the anatomy, histology, and development of the equine mammary gland underpins study of the pathology of diseases including galactorrhoea, agalactia, mastitis, and mammary tumour development. This review examines the prenatal development of the equine mammary gland and the striking degree to which the tissue undergoes postnatal development associated with the reproductive cycle. The gland is characterised by epithelial structures arranged in terminal duct lobular units, similar to those of the human breast, supported by distinct zones of intra- and interlobular collagenous stroma. Mastitis and mammary carcinomas are two of the most frequently described equine mammary pathologies and have an overlap in associated clinical signs. Mastitis is most frequently associated with bacterial aetiologies, particularly Streptococcus spp., and knowledge of the process of post-lactational regression can be applied to preventative husbandry strategies. Equine mammary tumours are rare and carry a poor prognosis in many cases. Recent studies have used mammosphere assays to reveal novel insights into the identification and potential behaviour of mammary stem/progenitor cell populations. These suggest that mammospheres derived from equine cells have different growth dynamics compared to those from other species. In parallel with studying the equine mammary gland in order to advance knowledge of equine mammary disease at the interface of basic and clinical science, there is a need to better understand equine lactational biology. This is driven in part by the recognition of the potential value of horse and donkey milk for human consumption, particularly donkey milk in children with ‘Cow Milk Protein Allergy’.

Mesothelial Cysts

Objectives Peritoneal mesothelial cysts have been reported under various terms, including benign cystic mesothelioma, usually in the form of case reports/series, whereas extraperitoneal cases are rarely reported. Our objective was to report the detailed characteristics of cystic lesions of the serosal cavities. Methods We retrospectively examined the clinicopathologic findings of a series of mesothelial cystic lesions (n = 79). Results Most cases (n = 68, 86%) concerned the peritoneum, whereas 11 (14%) concerned the pericardium. No pleural cases were found. A total of 51 (64.5%) lesions were solitary, whereas 28 (35.5%) were multiple. Peritoneal lesions harbored a plump eosinophilic mesothelium and a loose connective stroma, whereas pericardial lesions showed a cuboidal/flattened mesothelium, collagenous stroma, intense inflammation, and other tissue types, like adipose and muscle tissue. Solitary peritoneal lesions are usually extrapelvic and found in older patients incidentally during other surgeries, whereas multiple lesions are found in younger patients and usually in the pelvis. The lesions show a benign clinical course with rare recurrences but no malignant transformation. Conclusions Most mesothelial cysts are peritoneal and rarely pericardial. Peritoneal cysts differ from pericardial cysts. Peritoneal solitary lesions differ from multiple lesions, also suggesting their pathogenetic differences.

Conjunctival Stromal Tumor: Report of 2 New Cases and Review of the Literature

Conjunctival stromal tumor (COST) is an emerging entity with only a limited number of cases reported in the literature. In this report, we describe 2 additional cases, review the accumulative clinical and histopathological features and expand on the immunophenotypic property of this entity. COST appears to have a sporadic presentation, affecting both sexes and patients of variable ethnicity and age group and predominantly occurring on the bulbar conjunctiva as a slow-growing asymptomatic or slightly tender mass-like lesion. Histopathologically, COST is characterized by singly dispersed spindle to round cells, often with some degree of degenerative nuclear atypia, within a myxomatous to collagenous stroma. Lesional cells are characteristically positive for CD34 and vimentin, negative for S100, SOX10 and STAT6 and show a normal pattern of staining with RB1 by immunohistochemistry. The reported cases to date have shown an indolent biological behavior, reliably treated by a complete surgical excision.

The Enclosed Leviathan- Pleomorphic Fibroma

Cutaneous pleomorphic fibroma was initially described by Kamino et al in 1989 as a dermal, pauci-cellular neoplasm with an abundant fibrous tissue stroma, atypical fibro-histiocytic cells and disseminated multinucleated giant cells(1). Pleomorphic fibroma is an exceptional, benign, polypoid ordome shaped, sparsely cellular, cutaneous fibroblastic neoplasm characteristically delineating aberrant, pleomorphic, hyperchromatic and giant multinucleated cells embedded in a collagenous stroma (2). Pleomorphic fibroma is contemplated to originate from dendrocytes, in contrast to myofibroblasts. The exceptional neoplasm can simulate adjunctive fibro-histiocytic, melanocytic or lipomatous neoplasia. Despite cellular and nuclear atypia accompanying pleomorphic, bizarre cells, the neoplasm is contemplated as architecturally and biologically benign, on account of exceptional or absent mitosis(2). Pleomorphic fibroma may be interlinked with sclerotic fibroma. Martin-Lopez defined the terminology “pleomorphic sclerotic fibroma” which posits pleomorphic fibroma, sclerotic fibroma and pleomorphic sclerotic fibroma as neoplasia representing a morphologic continuum (3).