Inguinal Lymph Node Metastasis in a Case of Recurrent Biphasic Synovial Sarcoma - A Cytologic Diagnosis.

Synovial sarcomas (SS) are soft tissue tumors (STT) of unknown mesenchymal origin.[1] Not all sarcomas metastasize to lymph nodes with regional lymph node metastasis being less frequently encountered.[2] Here, we present cytologic diagnosis of a case of recurrent SS with an inguinal lymph node metastasis.

A 33-year-old male presented with pain in the left foot for the last 3 months. Examination revealed a scar over the left foot and minimal inguinal lymphadenopathy. Ultrasonography (USG) of the left inguinal region showed enlarged lymph nodes; one with necrotic center suspicious of metastatic deposit. USG-guided FNAC from the same showed moderately cellular smears comprising of loosely cohesive clusters of oval to spindle cells, nuclear atypia, bland chromatin, inconspicuous nucleoli and minimal pleomorphism [Figure 1a and b]. A distinct second population of round cells arranged in acinar pattern were recognized, having central to eccentric, round nuclei, fine nuclear chromatin and scant to moderate cytoplasm [Figure 1b, inset]. Few bare nuclei, mast cells and reactive lymphoid cells were also seen along with necrosis, suspicious of a metastatic spindle-cell sarcoma. A detailed history revealed a similar history 3 years back for which he was operated twice. Previous biopsy and immunohistochemistry slides were reviewed which revealed a high-grade biphasic-SS, positive for vimentin, CK7, epithelial membrane antigen(EMA), CD99, Bcl-2 and negative for S-100 and smooth muscle actin (SMA) [Figure 1c-h]. As the FNAC material was insufficient, ancillary techniques could not be performed. He defaulted chemotherapy and had presented after an interval of 11 months, so possibility of a metastatic biphasic-SS was suggested. Patient was referred for adjuvant therapy.

Figure 1

Cytosmears showing high cellularity with loosely cohesive clusters of spindle cells with thin vascular fragments (a), dyscohesive cell, singly lying ovoid to spindle cells showing minimal pleomorphism (b). Inset (b) shows round tumor cells showing glandular pattern of arrangement. Histopathology showed spindle cells (c) with expression of vimentin (d), CD99 (e), EMA (f), Bcl-2 (h) and negative for S-100 (g). [a-h: 400X]

SS is a STT, manifesting epithelioid differentiation. Earlier understanding suggested that the tumor took origin from synovium, while the current understanding recategorizes the same as an STT of uncertain differentiation.[1] It is a high grade, relatively chemoresponsive tumor with a specific translocation t(x; 18) (p11.2; q11.2).[3] Sarcomas metastasize conventionally through the hematogenous route. Those which spread to lymph nodes include rhabdomyo-, angio-, clear cell, epithelioid- and synovial-sarcoma. This case is unusual in exhibiting nodal metastasis as SSs show it in 1-50% cases.[245] Current guidelines recommend SSs to be classified in an intermediate-group called the 'potential-risk' histology. Lymph node involvement is poor prognostic factor, sign of dissemination and aggressiveness.[5]

SSs are hypercellular with cohesive clusters, monotonous oval bland nuclei, granular chromatin and prominent nucleoli. Mitoses, necrosis or even rhabdoid cells may be noted.[13] In this particular case, it has been highlighted that in biphasic-SS, tumor cells may be in glandular pattern with mast cells in a reactive lymphoid background. Presence of epithelial component helps but is infrequent. Presence of myxoid stroma and heterogeneous lesions helps in distinguishing SS from myoepithelial carcinomas.[6] 'Cigar-shaped' and 'buckled' nuclei help in differentiating from leiomyosarcoma and malignant peripheral nerve sheath tumor, respectively.[6] SSs express vimentin, cytokeratin, EMA and Bcl-2 while they are negative for SMA and S-100.[6] As is shown by this case, USG can be beneficial in evaluation, aspiration and biopsies of suspicious lymph nodes.[5] In addition, this case emphasizes a detailed clinical history and careful cytomorphologic assessment to identify the biphasic components along with soft pointers, use of immunomarkers and biopsy correlation for making an accurate diagnosis.

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