Histiocytic sarcoma arising from a lymph node: a diagnostic conundrum.

Histiocytic Sarcoma (HS) is extremely rare, with only a few hundred cases reported in the literature. The majority of patients present with symptoms due to unifocal or multifocal extra-nodal disease. Less than 20% of these cases show solitary involvement of a lymph node. We report a case of a solitary HS in a 53-year-old woman presenting with a 2.7-cm right groin mass arising from an inguinal lymph node. The initial cytologic examination of the tissue showed a high-grade spindle-shaped morphology with high-grade mitotic activity. A high-grade sarcoma was initially considered considering the absence of normal lymphoid aggregate and the presence of high-grade cytologic features in the cells. To evaluate the tumor in its entirety, the mass was surgically excised. A histological examination of the tumor showed focal rimming of the lymphoid tissue at the periphery and a centrally located stellate necrotic focus. The tumor cells had an epithelioid to spindle cell morphology along with large uniform nuclei and prominent nucleoli. A high mitotic index was present. Immunohistochemistry (IHC) stains showed strong positivity for CD68, CD163, and Vimentin, and were weakly positive for SMA and CD45. Based on the histologic and clinical examination, a diagnosis of HS was made. Multiple malignancies can mimic HS histopathology and the rarity of this tumor makes the diagnosis more challenging. No fine-needle aspiration (FNA) criteria for its diagnosis have been recognized. Herein, we report a rare case of an isolated HS involving a lymph node which resembled high-grade sarcoma on the FNA biopsy to raise awareness among our surgical pathologist colleagues.

Burkitt-Like Lymphoma with 11q Aberration: A Case Report and Review of a Rare Entity.

Burkitt-like lymphoma with 11q aberration is a rare diagnostic entity commonly occurring in children and young adults with a nodal presentation. This entity shares many similar morphologic and immunophenotypic features with conventional Burkitt lymphoma and other aggressive B-cell lymphomas, making its recognition challenging. However, the presence of its characteristic 11q gain/loss pattern is helpful in the diagnosis. We report a case of Burkitt-like lymphoma presenting as a right neck mass in a 17-year-old female patient that demonstrated no improvement with antibiotic therapy. The neoplasm displayed a diffuse proliferation of intermediate-sized atypical lymphoid cells with prominent nucleoli in a background of apoptotic debris, morphologically raising concern for conventional Burkitt lymphoma. Subsequent immunohistochemical and cytogenetic studies established the most likely diagnosis of Burkitt-like lymphoma with 11q aberration. Though rare, Burkitt-like lymphoma exhibits significant morphologic overlap with other high-grade B-cell lymphomas, making it an important entity to consider on the differential diagnosis of these lesions.

Subcutaneous desmoplastic small round-cell tumor: An unusual primary location expanding the differential of superficial round-cell tumors.

Desmoplastic small round-cell tumor (DSRCT) is a rare, aggressive malignant tumor, which in the great majority of cases arises at abdominal-pelvic sites. Nevertheless, rare cases of primary extra-abdominal tumors have been reported. In challenging cases, its molecular hallmark, the EWSR1-WT1 reciprocal translocation, can be exploited diagnostically by various molecular techniques. Herein, we report an extremely rare case of primary subcutaneous DSRCT in an effort to raise awareness among our dermatopathology colleagues by expanding the differential of superficial round-cell tumors.