Carcinosarcoma ex non-recurrent pleomorphic adenoma composed of TTF-1 positive large cell neuroendocrine carcinoma and myofibrosarcoma: apropos a rare Case

Abstract

We present a carcinosarcoma ex non-recurrent pleomorphic adenoma composed of a large cell neuroendocrine carcinomatous component and a spindle cell sarcoma with myofibroblastic differentiation. The tumor contained a hyalinized transition zone where the classical PA appeared to acquire two different histopathological patterns of malignant transformation of the epithelial component. The carcinomatous component was strongly and diffusely positive for low-molecular weight cytokeratins (AE1-3), synaptophysin, thyroid transcription factor-1 and focally positive for chromogranin A. All these markers were negative in the sarcomatous component. The sarcomatous component displayed immunoreactivity for smooth muscle actin with a predominantly linear, subplasmalemmal pattern. No expression of CD31, S100 protein, h-caldesmon, desmin, CD34, p63, myogenin, Myo D1 and c-kit was detected. Strong immunohistochemical expression of p53 was documented in both the carcinomatous and sarcomatous components as well as in the atypical epithelial component in the transition zone associated with the hyalinized pleomorphic adenoma.

Fig. 1

Photomicrograph of the gross surgical specimen showing a relatively well circumscribed tumor with a white–gray to tan cut surface. Large parts of the tumor showed haemorrhagic necrosis

Fig. 2

Haematoxylin and eosin stained sections revealed a distinctly biphasic appearance with a nested, carcinomatous component intimately intermingled with a spindle cell, sarcomatous component (a). The carcinomatous component showed high-grade malignant histological features including prominent nuclear atypia, high nuclear to cytoplamic ratio and abundant mitotic activity (b). The sarcomatous component displayed significant nuclear atypia and mitotic activity, including atypical forms (arrow; c). Areas with the classical features of a pleomorphic adenoma were present (d). The pleomorphic adenoma was associated with areas of hyalinization. The hyalinized areas of the pleomorphic adenoma (right) merged with a component of the tumor that had a “less orderly” appearance (left; e). This “less orderly” area contained a clearly atypical epithelial component. The epithelium displayed in addition to nuclear atypia a clear to vacuolated cytoplasm and a mostly readily identifiable peripheral myoepithelial layer (f). A mammary type of intraductal dysplasia/ductal carcinoma in situ-like proliferation which was invested by myoepithelial cells was also identified (g)

Fig. 3

Photomicrographs from the immunohistochemical study showing that the carcinomatous component was positive for cytokeratins (a), synaptophysin (b) and TTF-1 (c), while the sarcomatous component was negative. The sarcomatous component displayed immunoreactivity for SMA (d). The presence of smooth muscle actin positive myoepithelial cells displayed a gradual reduction to complete absence in the atypical epithelial component in the hyalinized area (e)