Scope of FNAC in the diagnosis of soft tissue tumors--a study from a tertiary cancer referral center in India

Abstract

Background: Fine needle aspiration cytology (FNAC) forms one of the first diagnostic tools in the evaluation of tumors. Its role in diagnosing soft tissue tumors (STT) has been fairly documented, as well as debated. Present study was aimed at evaluating its scope in diagnosing 127 cases of soft tissue tumors.

Methods: Conventional Pap and MGG staining was available in all the cases. Immunocytochemistry (ICC) was performed in 15 cases. Histopathological details were available in 115 cases.

Results: 50% cases were referred for a primary diagnosis, while 26.8% & 22.8% cases were evaluated for recurrent and metastatic lesions, respectively. Extremities were the commonest sites. On FNAC, 101 cases (79.5%) were labeled as malignant, whereas 10 cases (7.9%) were labeled as benign. The remaining 16 cases (11%) were not categorized and were labeled as 'unsure/not specified'. Histopathological confirmation in 115 cases, gave a diagnostic accuracy of 98%, with a positive predictive value of 98% in malignant cases and a negative predictive value of 100% in benign cases. Two cases were false positive. Among the various cytological categories, 60 cases (47.2%) were of spindle cell type, followed by 32 (25.2%) of round cell type and 14 cases (11%) of lipomatous type. Other 12 cases (9.4%) were of pleomorphic type; 7 (5.5%) cases of epithelioid type and remaining 2 cases were of myxoid type. All the round cell, pleomorphic and myxoid type of tumors were sarcomas, whereas 73.3% cases of spindle cell type were labeled as 'malignant'. Exact cytological sub typing was offered in 58 cases, with rhabdomyosarcoma (RMS) as the most frequently sub typed tumor. The two false positive malignant cases were of fibromatosis and a pigmented schwannoma, on biopsy. Out of 28 metastatic lesions, lymph nodes were the commonest site for metastasis, with epithelioid tumors that formed highest percentage of metastatic cases.

Conclusion: FNAC is fairly specific and sensitive in STT diagnoses for primary, recurrent and metastatic lesions. The cytological types, especially round cell and pleomorphic sarcomas, can be quickly identified. Clinicopathological correlation with ICC as an adjunct, are valuable in exact sub typing.

Figure 1

A. Pleomorphic lipoma. Mature adipose tissue fragments with giant cells (arrow). MGG × 200. B. High power view of 'Floret-type' giant cells, displaying 'wreath-like' nuclear arrangement. MGG × 400. C. Biopsy of pleomorphic lipoma displaying floret-type giant cells. H&E × 200. D. Myxoid Liposarcoma. Abundant metachromatic, myxoid stroma with vacuolated cells (Lipoblasts) (arrow). MGG × 400. E. Cellular smear showing plexiform capillary network with entrapped lipoblasts (inset) Pap × 200. F. Pleomorphic liposarcoma. Hypercellular smear showing several pleomorphic cells (arrow), including lipoblasts admixed with inflammatory cells. Pap × 400.

Figure 2

A. Rhabdomyosarcoma (RMS). Hypercellular smear with round cells, including plasmacytoid and binucleate forms (arrow), against a 'lacy' background MGG × 200. B. Smear with singly scattered round cells and an isolated strap cell/tumor rhabdomyoblast (arrow). Pap × 200. C. Diffuse desmin positivity in the round cells. DAB × 400. D. Alveolar RMS. Hypercellular smear with round cells including 'wreath'-like giant cells (inset). Pap × 400. E. High power view of an isolated wreath-like giant cell. Pap × 400. F. Cell block preparation showing strong myogenin expression. DAB × 400. G. PNET. Hypercellular smear with round cells, scattered singly and forming 'rosettes' (arrow). H. Positive MIC2 (CD99) expression in the tumor cells (DAB × 400). I. Neuroblastoma. Smear displaying round cells, with fine nuclear chromatin and exhibiting Homer-wright rosettes. J. High power view of an isolated pseudo rosette. L. Granulocytic sarcoma (formed on biopsy). Malignant round cell tumor, showing blasts. Strong MP0 positivity, on imprint, in the tumor cells. (DAB × 200).

Figure 3

A. Malignant peripheral nerve sheath tumor. Hypercellular smear showing loosely cohesive spindly cells with indented, 'serpentine' nuclei Pap × 400. B. Tumor cells showing S-100 positivity on cellblock preparation. DAB × 400. C. Leiomyosarcoma. Hypercellular smear showing fragments and singly scattered cells with blunt-ended nuclei. Pap × 400. D. Endometrial stromal sarcoma (ascertained on biopsy). Hypercellular smear with ovoid cells and abundant metachromatic basement membrane material. MGG × 200. F. Synovial sarcoma. Hypercellular smear with oval to elongated cells exhibiting overlapping. Pap × 200. G. A recurrent synovial sarcoma showing biphasic cellular pattern and eosinophilic material on smears. MGG × 400. H. Melanoma of soft parts. Cellular smear with spindly cells displaying prominent nucleolisation (inset). Pap × 400. I. Strong S-100 positivity on smears. DAB × 400 (Inset, S-100 highlighting spindly processes. DAB × 1000). J. Myxofibrosarcoma. Moderately cellular smear with oval cells admixed with metachromatic myxoid stroma. MGG × 200. K. Curvilinear vascular pattern with cells around. MGG × 400. L. Pleomorphic Rhabdomyosarcoma. Hypercellular smear with markedly pleomorphic cells. Pap × 400. Inset showing a pleomorphic rhabdomyoblastic cell. Pap × 400. M. Pleomorphic sarcoma not otherwise specified (NOS). Hypercellular smear with markedly pleomorphic cells against a hemorrhagic background. MGG × 400.

Figure 4

Tumors with epithelioid/polygonal shapes, exactly categorized on biopsy. A. Epithelioid sarcoma (recurrent case). Hypercellular smear with polygonal cells, scattered singly, displaying fine vacuoles in a minority of cells (inset). Pap × 400. B. Anaplastic large cell lymphoma. Hypercellular smear with singly scattered cells revealing moderate to abundant, eosinophilic to finely vacuolated cytoplasm and pleomorphic nuclei. MGG × 400. C. Malignant granular cell tumor. Hypercellular smear with loosely cohesive and singly scattered cells exhibiting ovoid nuclei and abundant, granular, eosinophilic cytoplasm. Pap × 200. C. Diffuse S-100 positivity in tumor cells on IHC on biopsy. DAB × 200.