WT1 and Cyclin D1 Immunohistochemistry: A Useful Adjunct for Diagnosis of Pediatric Small Round Blue Cell Tumors on Small Biopsies

Pediatric small round blue cell tumors (SRBCTs) are a heterogeneous group of neoplasms with overlapping morphological appearance. Accordingly, their diagnosis is one of the most difficult in the field of surgical pathology. The most common tumors include rhabdomyosarcoma, Ewing’s sarcoma, neuroblastoma, lymphoblastic lymphoma and Wilms’ tumor (the blastemal component). Over time their diagnosis has become more difficult due to the increasing use of small biopsies. However, the advent of immunohistochemistry has improved the quality of diagnosis in most cases by the application of an adequate panel of immunomarkers. Recently, WT1 and Cyclin D1 have been shown to be useful in the differential diagnosis of SRBCTs on surgically-resected specimens, showing a diffuse cytoplasmic positivity of the former in all RMSs and a diffuse nuclear staining of the latter in both EWS and NB. The aim of the present study was to investigate the expression of WT1 and Cyclin D1 on small biopsies from a series of 105 pediatric SRBCTs to evaluate their diagnostic utility. Both immunomarkers were differentially expressed, with a diffuse and strong cytoplasmic staining for WT1 limited to all cases of RMS, and a diffuse nuclear staining for cyclin D1 restricted to all cases of EWS and NB. Notably, the expression of WT1 and cyclin D1 was also retained in those cases in which the conventional tumor markers (myogenin, desmin and MyoD1 for RMS; CD99 for EWS; NB84 for NB) were focally expressed or more rarely absent. The present study shows that WT1 and Cyclin D1 are helpful immunomarkers exploitable in the differential diagnosis of pediatric SRBCTs on small biopsies, suggesting their applicability in routine practice.

Glioblastoma multiform with primitive neuronal component, radiological and histology features: a case report

Background Glioblastoma multiform with primitive neuronal component (GBM-PNC) has been recently defined as a rare variant of glioblastoma multiform (GBM), which shows characteristically pathological pattern of less differentiated areas with small blue cell morphology and neuroectodermic immunophenotype. New studies emphasize its characteristics and differences, which have become vitally important due to the changes in therapeutic management. Case presentation We present the case of 57-year-old male patient who onset symptoms were secondarily widespread partial seizures and expression aphasia. Brain magnetic resonance imaging (MRI) reported left enhanced temporal infiltrating lesion, requiring surgery twice throughout two years. At first surgery, pathological samples revealed embryonic tumor of the central nervous system (grade IV, WHO 2016), so PACKER protocol consisting of CSRT (craniospinal radiation) plus weekly vincristine followed by 8 cycles of cisplatin, lomustine and vincristine usually used for medulloblastomas or other primitive neuroectodermal tumors was started. However, due to reappearance of symptoms and progression in MRI, reoperation was performed with definitive diagnosis of GBM-PNC (Grade IV, WHO 2016) and switched to STUPP protocol. Conclusions It is important to take into account the chance of this entity when histological, radiological and intraoperative findings orient toward a primitive neural tumor since the presence of GBM could be overlooked leading to mistakes in diagnosis and the therapeutic orientation.

Role of CD200 in the Detection of Nonhematologic Neoplasms by Routine Flow Cytometry Analysis

Objectives While flow cytometry is routinely used in the diagnostic work-up of hematolymphoid malignancies, its role in identifying non-hematolymphoid neoplasms is controversial. While a diagnosis of “non-hematolymphoid process” may be suggested by flow cytometry, typically, CD45-negative entities are not further characterized by their immunophenotypic profile. Some markers, such as CD56, have been well documented in non-hematolymphoid malignancies, such as high-grade neuroendocrine carcinomas (Stacchini, et al, 2018; Bryson et al, 2002). Other cell surface markers that are routinely studied with flow cytometry panels, such as CD200, are less well-described in the literature with regards to their presence/absence in non-hematolymphoid processes. We examined all flow cytometry cases from our institution over a 5-year period to identify trends in the immunophenotypes of non-hematolymphoid malignancies that were known to be CD45-negative and CD56-positive by flow cytometry. Methods We examined 3634 flow cytometry cases (2015-2020) and identified non-hematolymphoid cases based upon lack of CD45 expression. After excluding multiple myeloma cases from the CD45-negative entities, we were left with 19 CD45-negative cases. Chart review of these cases confirmed them as non-hematolymphoid by concurrent surgical pathology/cytopathology studies. Of these 19 cases, 2 were excluded because CD56 was not evaluated. Results Of the 17 CD45-negative/CD56-positive cases, 16 showed CD200 positivity (94%). Of these CD200-positive cases, 10 were ultimately diagnosed as small cell carcinoma (59%), 1 was diagnosed as Merkel cell carcinoma (6%), 1 was diagnosed as melanoma (6%), 1 was diagnosed as poorly-differentiated carcinoma (6%), 1 was diagnosed as Ewing-like sarcoma (6%), and 2 were unclassified further (12%). The single CD200-negative case was diagnosed as poorly-differentiated acinar cell carcinoma (6%). All cases of small cell carcinoma that were evaluated by flow cytometry showed expression of CD200 and CD56. Conclusions Our findings suggest that in CD45-negative/CD56-positive non-hematolymphoid malignancies, particularly small cell carcinoma, CD200 is frequently positive. CD200 was also found to be positive in rare cases of other non-hematolymphoid malignancies within the differential diagnosis of small round blue cell tumors. These findings indicate that CD200 may be a useful marker in suggesting the possibility of small cell carcinoma in non-hematolymphoid specimens that are evaluated by flow cytometry.

Primary primitive neuroectodermal tumor of the adrenal gland: A unique tumor at an unusual site

Ewing sarcoma/Primitive Neuroectodermal Tumor (ES/PNET) is a malignant small round blue cell tumor of neuroectodermal origin that affects bones and soft tissue in children and young adults. ES/PNET is very uncommon in parenchymal organs. We report a case of primary adrenal PNET in a young female having pregnancy induced persistent hypertension. She underwent right adrenalectomy for a large adrenal mass. On histopathology, it was typical malignant round cell tumor (MRCT). Immunohistochemistry confirmed the diagnosis of ES/PNET with expression of CD99, FLI-1 and NKX2.2. Until now, only 38 cases of primary adrenal ES/PNET have been reported in the English literature with just 5 cases from India. Adrenal ES/PNET can be mistaken with other MRCTs like Non-Hodgkin lymphoma and neuroblastoma. Since the biology, treatment and prognosis of these tumors is entirely different, we emphasize that pathologists must be aware of this possibility and try to differentiate them using ancillary techniques.

Pediatric Small Round Blue Cell Tumors: Cytopathological Puzzle or an Intriguing Scientific Window?

<b><i>Background:</i></b> Small round blue cell tumors or more commonly called small round cell tumors (SRCTs) are undifferentiated neoplasms, sharing an overlapping morphological pattern of small round blue cells. Diagnosing these tumors represents a complex challenge for cytopathologists and for general surgical pathologist alike. This stems from the fact that these tumors share not only similar morphological features, but also some immunophenotypic characteristics, thus requiring a broad panel of antibodies, which might not be included in the most basic immunohistochemistry panels, used in the routine work of most pathology laboratories. Furthermore, one should note that the diagnosis, prognosis, and/or therapeutic decision are often dependent on the knowledge of the existence of specific molecular alterations, which requires access to sophisticated molecular ancillary techniques. Cytological diagnosis of SRCT should be systematized. A thorough understanding of the morphological pattern of these tumors, the small details they entail, the background and cellular patterns, and the nuclear and cytoplasmic peculiarities, may hint to the most probable diagnosis. Minor clues, such as the presence of a fibrillar background, the presence of rosettes or a specific “salt and pepper” chromatin, are important clues toward a probable diagnosis of a neuroblastoma, or the presence of a tigroid background is a characteristic of rhabdomyosarcoma and the Ewing family tumors. However, in poorly differentiated tumors, morphology alone will not suffice, making it essential for the access to complementary diagnostic techniques in order to reach the final diagnosis. <b><i>Summary and Key Messages:</i></b> The cytological diagnosis and treatment of SRCTs require an experienced, well-articulated, proficient teamwork, and sophisticated complementary diagnostic techniques, only available in centers of reference.

Detection of BCOR gene rearrangement in Ewing-like sarcoma: an important diagnostic tool

Background BCOR-CCNB3 sarcoma (BCS) is a group of undifferentiated small round cell sarcomas harboring the BCOR gene rearrangement which shares morphology with the Ewing sarcoma family as well as other malignant round blue cell tumors, thus making them difficult to diagnose. The aim of this study was to explore the role of molecular techniques in the diagnosis of BCS. Methods Twenty-three cases of EWSR1 rearrangement-negative undifferentiated small round cell sarcomas (Ewing-like sarcoma) were analyzed for the presence of BCOR gene rearrangement by Fluorescence in situ hybridization (FISH) and Reverse Transcription -Polymerase Chain Reaction (RT-PCR). The clinicopathological features of the positive cases were also reviewed. Fifteen additional cases were used as negative controls. Results Eight cases were found with BCOR gene rearrangement by FISH and reappraised as BCS. The patients ranged in age from 8 to 20 years old, with a male predominance (M:F = 6:2). All tumors were located in the lower extremities. The tumor locations were more common in bone (n = 6) than deep soft tissue (n = 2). Histologically, 7 of 8 tumors were predominately composed of spindle or ovoid cells. The tumor cells were usually arranged in solid hypercellular sheets without a distinct architectural pattern. IHC showed expression of TLE1 (100%), CCNB3 (88%), BCOR (71%). RT-PCR for BCOR-CCNB3 fusion transcript was positive in 7 of 8 cases. Pre-operative chemotherapy resulted in eradication of tumors in 5 patients after a follow-up of 7 to 42 months. Conclusions Efficient diagnosis of BCOR rearranged sarcomas is achieved by the using a combination of FISH and RT-PCR assays.