Chondroblastoma-like chondroma of soft tissue: report of the first case in the base of skull.

Chondroblastoma-like chondroma (CLC) of soft tissue is a rare benign neoplasm that usually involves the soft tissues of the hand. This report describes the first case of CLC of soft tissue arising in the base of the skull. A 33-year-old man was seen with a slow growing mass in the right parotid region of his face. The noncontrast computed tomographic scans showed an 8.5-cm mass with calcifications involving the right masticator space and extending through the bone into the middle cranial fossa. The radiologic differential diagnosis included osteosarcoma, leiomyosarcoma, chondrosarcoma, and giant cell tumor. During surgery, the large lateral skull base tumor appeared to involve the middle and infratemporal fossae and eroded the surrounding bone. Although the tumor was removed piecemeal, total excision was performed. On microscopic examination, the tumor displayed lobules of mature hyaline cartilage with numerous chondroblasts, coarse calcifications including chicken wire calcifications, and scattered osteoclasts. No atypia, mitoses, necrosis, or osteoid formation was seen. The tumor was diagnosed as chondroma with chondroblastoma features of the soft tissue. His postoperative clinical course was uneventful; however, after 7 months, he had a local recurrence identified on follow-up magnetic resonance imaging. He underwent repeat surgical excision of the tumor, which showed similar histology as the previous excision. This large skull based tumor eroding the bone, which clinically and radiologically mimicked a malignant process, was an unusual presentation of a benign cartilaginous neoplasm. Pathologists should be aware that CLC may occur in the base of the skull and this lesion should be differentiated from the other benign or malignant tumors arising in this area. These lesions have a potential for local recurrence; hence, a close follow-up is recommended.

Carcinoma In Situ Involving Sclerosing Adenosis on Core Biopsy: Diagnostic Pearls to Aid the Practicing Clinician and Avoid Overtreatment.

INTRODUCTION: Involvement of pre-existing benign lesions by ductal carcinoma in situ (DCIS) or lobular neoplasia (LN) can present difficult diagnostic challenges, and can easily cause misdiagnosis of invasive carcinoma and over-management of localized disease. Our objective was to gather the largest case series of DCIS and LN involving sclerosing adenosis (SA), and to report the characteristic features of these lesions, in order to provide histologic criteria for the diagnostician. METHODS: Our database was searched for core biopsy material diagnosed as carcinoma in situ involving adenosis. Glass slides and pathology reports were reviewed. The cases were studied for salient features, and clinical follow-up was also obtained. RESULTS: Thirty-one cases of DCIS or LN involving SA were obtained (12 cases of DCIS, 19 cases of LN including LCIS and ALH). Histomorphologic features commonly seen with DCIS or LN involving SA included lobulocentric architecture (31/31, 100%), myoepithelial cells visible by H&E at least focally (31/31, 100%), and separate areas of SA not involved by neoplasia (29/31, 93.5%). Features that were sometimes seen included hyaline basement membranes surrounding the lesion (14/31, 45.2%), DCIS/LN apart from the area of involvement by SA (16/31, 51.6%), and calcifications associated with DCIS/LN/SA (12/31, 38.7%). Features that were not commonly seen included desmoplasia (6/31, 19.4%), dense inflammation (4/31, 12.9%), and single epithelial cells enveloped by flattened myoepithelial cells (6/31, 19.4%). Of the ten cases of DCIS with known follow-up, four showed DCIS involving either SA or a complex SA on excision (4/10, 40%), four had only DCIS (4/10, 40%), one had DCIS with a small 1.8-mm focus of predominantly tubular carcinoma (1/10, 10%), and one showed invasive ductal carcinoma on excision (1/10, 10%). The latter case of invasive ductal carcinoma occurred in a patient who had a delay of 3 years from diagnosis to surgical resection. Of the eight cases of LN with surgical follow-up, seven had LCIS (7/8, 87.5%), and one showed only fibroadenoma and SA with no residual LN in the excised specimen (1/8, 12.5%). Importantly, no invasive carcinoma was identified in any of the resections for LN involving SA. CONCLUSIONS: In our series of carcinoma in situ (CIS) involving sclerosing adenosis diagnosed on core biopsy, lobular lesions involving SA were more common than ductal lesions. Ductal and lobular carcinoma in situ involving adenosis were best diagnosed by the low-power appearance of a lobulocentric pattern of growth. The most helpful diagnostic feature was the observation of additional foci of carcinoma in situ away from the adenosis. Immunohistochemical stains for myoepithelial cells were useful in particularly difficult cases. The presence of stromal desmoplasia does not preclude the diagnosis of carcinoma in situ involving adenosis. Knowledge of these diagnostic pearls can reduce over-interpretation of CIS on core biopsy and subsequent overtreatment.