Mechanical Forces during Lymph Node Expansion Govern Fibroblastic Reticular Network Remodeling

After immunogenic challenge, the lymph node rapidly increases in cellularity making space for infiltrating and dividing lymphocytes, expanding the tissue. In the early phases of expansion, the underlying fibroblastic stroma, which organises the lymph node, undergoes elongation and stretching. This is followed by the initiation of fibroblastic stroma proliferation as inflammation proceeds. In the steady state, fibroblastic reticular cells (FRCs) tightly wrap an interconnected network of extracellular matrix fibres. The initial physical deformability of the lymph node is in part determined by Podoplanin (PDPN) signalling in FRCs and is modulated by dendritic cells expressing C-type lectin receptor 2 (CLEC-2). However, the mechanisms changing tissue and cellular mechanical forces of the fibroblastic stroma and the triggers for FRC proliferation and growth are unknown. We examined the contributions of FRC actomyosin contractility and extracellular matrix to lymph node tissue tension. Further, we directly tested the impact of tissue mechanics on the kinetics of lymph node expansion. We show using laser ablation that the FRC network is under mechanical tension generated by actomyosin contractility and that tension changes throughout the course of immunogenic challenge. We find that CLEC-2/PDPN signalling alters the cell intrinsic mechanical state of FRCs by reducing cortical tension and increasing FRC size. We found that FRC network tension is a critical cue in controlling lymph node expansion gating the initiation of FRC proliferation. Together this study demonstrates mechanical forces are generated and sensed through the FRC network to determine lymph node expansion required for an adaptive immune response.

Analogous feature of cemento-ossifying fibroma and bone pathology: a clinico-pathological correlation

Intra-osseous pathology of the craniofacial region is microscopically characterized by hypercellular fibroblastic stroma with a variable amount of bone or cementum like calcified structures. The overlapping histopathological features are not limited to lesions under one classification of similar origin rather it imbricates the lesions of entirely different origin as well. The only possible way out then becomes the clinicopathological correlation. Hence, in an out of entire clinical, a radiographic, surgical, and histopathological feature reframes the building block for confirmatory diagnosis of a bone lesion.

Histologic Findings of Uterine Niches

Objectives The disruption or defect of the myometrium in the uterine scar of a cesarean section (CS) has been known by various names, such as uterine niche, isthmocele, deficient uterine scar, scar pouch, or diverticulum. Symptomatology, risk factors for niche development, and available treatment modalities have been recently studied. However, the histologic features of this disease remain unknown. Methods The histologic features of eight uterine niches are thoroughly described and a summary of the most important aspects of the uterine niche literature is provided. Five cases of CS scars without niche formation are comparatively examined. Results Most uterine niches harbor endocervical mucosa, often cystically dilated and/or an atrophic or disorganized endometrial mucosa of lower uterine segment origin. Regenerative epithelial atypia and fibroblastic stromal reaction are frequent features. No granulomatous reaction, important inflammation, or hemorrhage is seen. CS scars without niche formation do not harbor endocervical mucosa or inclusion cysts, fibroblastic stroma, or regenerative atypia. Conclusions As more prospective studies of uterine niche development and treatment will be conducted, a detailed pathologic report with the criteria proposed herein can be designed.

Multicystic Nephroma-Report of Two Rare Cases in a Span Of Seven Years

Background: Multicystic nephroma (MCN) is an uncommon but distinctive benign pediatric renal neoplasm but may present clinically at any age. It is scantily reported in the literature. To the best of our knowledge it has not yet been reported from Nepal. It is characterized by a well circumscribed mass with nodular outer surface that contain multiple fluid filled locals. Microscopy show cystically dilated spaces lined by flattened to columnar epithelium and is separated by fibroblastic stroma. A hobnail pattern is common.Case description: Here we report two cases of multicystic nephroma in a span of seven years. The first case is of a one year old female child who was diagnosed of having huge left sided renal mass clinically and the second case is of a 35-year-old male revealing hydatid cyst in USG, CT scan and IVP. Both of them underwent nephrectomy and their microscopic examination revealed typical characteristics of a multicystic nephroma.Conclusion: Since MCN has a benign behaviour it must be differentiated from focal cystic neoplastic lesions, including cystic partially differentiated nephroblastoma (CPDN), which has a low but distinct capability for local recurrence; from Wilm’s tumour with cystic change; and cystic renal cell carcinoma.Health Renaissance 2014;12(3): 227-229

Equine Juvenile Mandibular Ossifying Fibroma

Benign proliferative fibro-osseous lesions of the rostral mandible in six young horses are classified as equine juvenile mandibular ossifying fibroma. Histologically there is a characteristic abrupt transition from subgingival fibroblastic stroma to a zone of proliferating osteoblasts that form irregular spicules of osteoid. The layer of proliferating osteoblasts blends with a deeper zone of bony trabeculae rimmed by osteoblasts and separated by intertrabecular spaces of moderate cellular density. Incomplete surgical excision resulted in local recurrence, while rostral mandibulectomies resulted in no recurrence. The predilection for the rostral mandible of young horses coupled with the similar clinical, radiographic, and histological characteristics supports the classification of this lesion as a distinct entity.