A Case of Metaplastic Squamous Cell Carcinoma of the Breast that Showed a Pathological Complete Response After Neoadjuvant Chemotherapy with Weekly Paclitaxel

Abstract

BACKGROUND Primary squamous cell carcinoma of the breast is a rare type of metaplastic breast carcinoma, characterized by resistance to conventional chemotherapy agents. We report a case of metaplastic squamous cell carcinoma of the breast in which a pathological complete response was achieved after neoadjuvant chemotherapy with weekly paclitaxel and in which the patient remained disease free for 15 years and 7 months. CASE REPORT A 40-year-old woman had a palpable 5-cm-diameter tumor in the right breast that was diagnosed as metaplastic squamous cell carcinoma of the breast based on core needle biopsy. The patient was initially treated with an adjuvant chemotherapy (AC) regimen consisting of doxorubicin (60 mg/m²) and cyclophosphamide (600 mg/m²) as neoadjuvant chemotherapy. Because the tumor grew rapidly and the skin redness increased after 1 cycle of the AC regimen, 12 cycles of weekly paclitaxel 80 mg/m² were subsequently administered. The tumor responded dramatically to paclitaxel. The patient underwent mastectomy with level II axillary lymph node dissection. No residual tumor cells were found, which indicated pathological complete response. The patient is currently disease free at 15 years and 7 months after the operation. CONCLUSIONS To our knowledge, there are no previous reports of metaplastic squamous cell carcinoma of the breast in which pathological complete response was achieved by treatment with neoadjuvant chemotherapy with weekly paclitaxel (80 mg/m²).

Figure 1.

(A) Mammography performed before chemotherapy demonstrated an indistinct, high-density mass with pleomorphic calcification in the upper portion of the right breast. (B) Magnetic resonance imaging (MRI) before chemotherapy showed a lobulated mass with irregular margins and rapid enhancement during the early phase of the enhanced kinetics. The image demonstrated washout of the enhancement pattern during the delayed phase. (C) Mammography performed after chemotherapy showed the marked shrinkage of the mass with a microlobulated and partially irregular margin. (D) MRI after chemotherapy showed that the mass was considerably reduced.

Figure 2.

Core needle biopsy specimen of the tumor. (A) A low-power view showed squamous cell carcinoma (HE, ×100). (B) A high-power view showed a nest of squamous cell carcinoma (HE, ×400). HE, hematoxylin and eosin.

Figure 3.

(A) Ultrasonography performed before the administration of weekly paclitaxel revealed a hypoechoic lesion with cystic components, measuring 7.7 cm. (B) Ultrasonography performed after chemotherapy showed that the size of the tumor was significantly decreased to 1.9 cm.

Figure 4.

(A) Macroscopic finding of the tumor. A cystic area measuring approximately 8 mm was observed. (B) Histopathological findings of the cystic area (HE, ×20). (C) The cyst wall (✶) was covered by foamy histiocytes and lymphocytic infiltration, including calcification and hemosiderin-laden macrophages (HE, ×100). (D) Only necrotic tissue and foamy histiocytes were observed inside the cyst (✱). No tumor cells were detected in the resected specimen (HE, ×100). HE, hematoxylin and eosin.