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CASE 2

 

DIAGNOSIS - CASE 2

 

A total of 11 answers for this case were divided as follows:

- 03: Pleomorphic lipoma
- 02: Dermatofibrosarcoma protuberans
- 01: Myxofibrosarcoma
- 01: Malignant fibrous histiocitoma myxoid
- 01: Fibromyxoid sarcoma
- 01: Angiomiofibroblastoma
- 01: Spindle cell lipoma
- 01: Superficial angiomyxoma

Send comments and questions about this case to:
Antonio F. Conde Martín
Hospital Can Misses
Ibiza- Spain

 
 

DISCUSSION - CASE 2

 
Histology:
The tumor shown in Case 2 shares a prominent mucoid matrix and characteristic pseudo-vascular spaces of irregular shape. Some multinucleated giant cells were seen in the limits of the pseudo-vascular spaces (Photos 1 & 2). There was no evidence of storiform pattern. No mitotic figures were found.

Discussion:
In view of the histological findings, nine different possibilities were considered:

- Myxoid liposarcoma
- Pleomorphic lipoma
- Myxoid malignant fibrous histiocytoma
- Myxoid fibrosarcoma
- Fibromyxoid sarcoma
- Myxoma
- Superficial angiomyxoma
- Dermatofibrosarcoma protuberans myxoid type
- Giant cell fibroblastoma

Myxoid liposarcoma is the most frequent type of liposarcomas (approximately 50% of all). It is composed of three major components: proliferating lipoblasts (in varying stages of differentiation), a delicate capillary plexiform pattern, and a myxoid matrix. These components can be seen in every tumor of this type. The present case lacks lipoblasts and the characteristic vascular pattern of fat tumors. The negativity of S-100 protein is also against this possibility.

Pleomorphic lipoma occurs as a well-circumscribed subcutaneous mass in the neck and the shoulder region. It can simulate a pleomorphic or sclerosing liposarcoma. The characteristic inflammatory elements, mitotic figures and floret like giant cells in this tumor are not seen in our case. Again, S-100 negativity is against this diagnosis.

Myxoid malignant fibrous histiocytoma has myxoid areas in association with characteristic areas of malignant fibrous histiocytoma. The vessels form arches with condensation of tumor and inflammatory cells. In our case, pseudo-vascular spaces (not true vascular spaces) are delineated by tumor cells. Also, no characteristic area of storiform pattern was seen.

Myxofibrosarcoma is one of the most common sarcomas in the extremities of elderly patients. Histological characteristics include myxoid matrix containing curvilinear capillaries and fusiform, round or stellate tumor cells with indistinct margins, eosinophilic cytoplasm, and hyperchromatic atypical nuclei. Tumors vary from purely myxoid fusocellular to highly cellular pleomorphic lesions. Even in lower grade lesions a significant proliferative activity is evident (MIB-1 positivity and high mitotic count).

Low-grade fibromyxoid sarcoma occurs in younger patients as compared with myxofibrosarcoma and it frequently metastasizes. Histologically is composed of fibrous and myxoid areas. A swirling, whorled pattern is demonstrable at least partially. Cellularity and cytological atypia is in general low.

Myxoma is mainly an intramuscular, infiltrative tumor that contains few vessels and lacks cellular atypia. Myxomas of superficial locations are usually found at juxta-articular locations, often associated with previous trauma.

Superficial angiomyxoma is a slow growing tumor localized in the dermis or subcutis without nuclear hyperchromasia and pleomorphism. Prominent blood vessels, some times dilated, are of valuable diagnostic help.

Giant cell fibroblastomas develop as painless nodules in the subcutis or dermis. They affect predominantly infants and children but are encountered infrequently in adults. They are composed of loosely arranged, wavy spindle cells with a moderate degree of nuclear pleomorphism that infiltrate and (in superficial cases) encircle adnexal structures in a fashion similar to dermatofibrosarcoma protuberans. Giant cell fibroblastomas vary in cellularity from those resembling dermatofibrosarcoma protuberans to those that are hypocellular with a predominant myxoid or hyaline stroma. The characteristic features of the tumor is the peculiar pseudo-vascular spaces lined by a discontinuous row of multinucleated cells. These tumors express vimentin but lack S-100. As dermatofibrosarcoma protuberans, some giant cell fibroblastoma express CD-34. Dermatofibrosarcoma protuberans may share some of the myxoid changes and the presence of giant atypical cells as seen in giant cell fibroblastoma. Based on similarities found on morphological studies, tumor recurrence and immunohistochemical markers, of both dermatofibrosarcoma protuberans and giant cell fibroblastoma, some authors have raised the possibility of a common origin. However, I consider that in predominantly myxoid tumors, to make a diagnosis of dermatofibrosarcoma protuberans we must find the presence of some storiform pattern.

After all these considerations, our diagnosis for Case 2 is of a Giant cell fibroblastoma.

SEND QUESTIONS ABOUT THIS CASE TO: Dr. Antonio F. Conde Martín

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