Primary squamous cell carcinoma, breast: A challenging diagnosis

Primary squamous cell carcinoma of the breast is an extremely rare malignancy constituting less than 0.1% of all breast cancers with very few cases reported in literature. It is an aggressive, triple-hormone negative tumor, and its appropriate management is still debated. It is diagnostically challenging on both histopathology as well as radiology. Different diagnostic criteria are established for its definite diagnosis. As squamous cells are not found normally in the breast, various theories have been proposed regarding its origin. But the exact pathogenesis is still unclear. We report one such case encountered.

A 54-year-old female presented with gradually progressive painless lump in the right breast for 3 months with no other clinical features. There was neither any history of chronic or malignant disease in the patient nor in her family. On clinical examination, there was well-defined, firm and nontender swelling in upper inner quadrant measuring 3 × 2 cm with overlying skin being normal. There was no swelling in the contralateral breast as well as in the bilateral axillary region. A suspicion of malignancy was raised on initial core needle biopsy and, on repeat biopsy, was diagnosed as metaplastic carcinoma with squamous differentiation. Later, on final resection, specimen was reported as primary squamous cell carcinoma of the breast without any nodal metastasis. All the metastatic causes were ruled out through proper clinical, radiological, and histopathological correlation.

Primary squamous cell carcinoma of the breast is an aggressive tumor with its treatment protocol being still unclear, owing to its rarity. It is important to rule out the metastatic causes. It is relatively resistant to conventional chemotherapy, and its prognosis is also unpredictable. Hence, this requires further studies in terms of management and prognosis.