Introduction
Benign fibrous histiocytoma (FH, dermatofibroma) is a common skin lesion and several histologic variants were identified including three major subtypes: cellular, aneurysmal and atypical. The primary lesion most frequently occurs in young adults, is located on the extremities and microscopically presents as a cellular FH. Its metastasizing variant is extremely rare and only 18 cases have been reported to date. Locoregional lymph nodes and (or) lung are typical sites of metastases. Case report
A 31-year-old female underwent resection of the inguinal lymph node, 3 cm in diameter, with a suspicion of metastasis. Two years before the resection, a cutaneous and subcutaneous lesion measuring 1.5 cm in diameter of the right thigh was excised (Fig. 1 A, B). There was no evidence of relevant family history of oncologic diseases. The microscopic findings of the lesion revealed a nodular, cellular proliferation involving dermis and extending into subcutis forming short, intersecting fascicles of fibroblastic spindle and ovoid cells with no nuclear atypia and low mitotic activity. The stroma was composed of a delicate collagen network (Fig. 1 C, D). The morphological features of metastasis to the lymph node were the same as the primary skin FH presented above (Fig. 1 A, B). The immunohistochemical stainings with anti CD34, S100 and desmin antibodies were negative. After three years of follow-up, the patient is alive with no symptoms of metastatic disease. Discussion
Benign fibrous histiocytoma of the skin is one of the most common entities diagnosed in the routine surgical pathology service. It represents a benign but diverse group of neoplasms which exhibits both fibroblastic and histiocytic features; however, its nature of differentiation is still uncertain. Several histologic variants were identified including three major subtypes: cellular, aneurysmal and atypical. A number of rare variants, i.e. lipidized (ankle-type), palisading, with myxoid, clear-cell or granular cell change. A minor group of FH has borderline histologic image demonstrating focal atypia and some mitotic activity; it was classified as atypical benign fibrohistiocytoma, which may recur locally and is thought not to metastasize. The differential diagnosis includes other benign lesions, i.e. nodular fascitis, neurofibroma and leiomyoma as well as dermatofibrosarcoma protuberans (DFSP). The most typical immunostaining for FH is positive reaction for factor XIIIa and negative or peripherally scant with CD34 antibody. Dermatofibrosarcoma protuberans expresses CD34 in a significant portion of neoplastic cells. Thus, a combination of these two immunohistochemical reactions is needed for differential diagnosis. In some cases, desmin or smooth muscle actin may be positive but the morphological features of FH are characteristic enough to avoid the diagnosis of a smooth muscle neoplasm. In vast majority of cases, no recurrence is observed once the lesion is completely removed but occasionally one or more recurrences are noted. In 1996, Colome-Grimmer reported two cases of FH designated as cellular [1]. One of the cases recurred several times and metastasized to the locoregional lymph node and lung. The other case metastasized to the lymph node and lung with no recurrence observed. In addition, the authors described histological features of FH that are associated with a tendency for recurrence and metastasis. The set of features includes: relatively large size, aneurysmal change, high cellularity, pleomorphism, high mitotic index and necrosis. Subsequently, more cases of the metastasizing FH have been reported [2-10]. In 2010, Luzar and Calonje reviewed cutaneous fibrohistiocytic tumours including all 12 cases of metastasizing FH available in the literature [11]. Deep FH is usually larger in diameter than the cutaneous or subcutaneous variant. It shows histological features similar to FH but rare haemangiopericytoma (HPC) pattern, fibrosis and necrosis are seen. Occasionally, deep FH may behave as an aggressive neoplasm. Among 69 cases of deep FH published by Gleason, two cases showed metastases and the patients ultimately died of the disease [2]. The primary skin lesion of the current case showed histological features of FH with bland spindle and ovoid cells, focal aggregates of foam cells, low mitotic index and no necrosis. An inguinal lymph node showed similar histological features intermingled with lymphoid tissue. Three years after initial diagnosis of the skin lesion, the patient shows no recurrence and no other metastatic lymph nodes. There is no evidence of distant metastasis. Table I shows a summary of the literature review which includes all 19 cases reported to date. References
1. Colome-Grimmer MI, Evans HL. Metastasizing cellular dermatofibroma. A report of two cases. Am J Surg Pathol 1996; 20: 1361-1367.
2. Gleason BC, Fletcher CD. Deep “benign” fibrous histiocytoma: clinicopathologic analysis of 69 cases of a rare tumor indicating occasional metastatic potential. Am J Surg Pathol 2008; 32: 354-362.
3. Guillou L, Gebhard S, Salmeron M, Coindre JM. Metastasizing fibrous histiocytoma of the skin: a clinicopathologic and immunohistochemical analysis of three cases. Mod Pathol 2000; 13: 654-660.
4. Gu M, Sohn K, Kim D, Kim B. Metastasizing dermatofibroma in lung. Ann Diagn Pathol 2007; 11: 64-67.
5. Osborn M, Mandys V, Beddow E, et al. Cystic fibrohistiocytic tumours presenting in the lung: primary or metastatic disease? Histopathology 2003; 43: 556-562.
6. De Hertogh G, Bergmans G, Molderez C, Sciot R. Cutaneous cellular fibrous histiocytoma metastasizing to the lungs. Histopathology 2002; 41: 85-86.
7. Kaddu S, McMenamin ME, Fletcher CD. Atypical fibrous histiocytoma of the skin: clinicopathologic analysis of 59 cases with evidence of infrequent metastasis. Am J Surg Pathol 2002; 26: 35-46.
8. Colby TV. Metastasizing dermatofibroma. Am J Surg Pathol 1997; 21: 976.
9. Joseph MG, Colby TV, Swensen SJ, et al. Multiple cystic fibrohistiocytic tumors of the lung: report of two cases. Mayo Clin Proc 1990; 65: 192-197.
10. Bisceglia M, Attino V, Bacchi CE. Metastasizing “benign” fibrous histiocytoma of the skin: a report of two additional cases and review of the literature. Adv Anat Pathol 2006; 13: 89-96.
11. Luzar B, Calonje E. Cutaneous fibrohistiocytic tumours – an update. Histopathology 2010; 56: 148-165. Address for correspondence
Anna Szumera-Ciećkiewicz MD
Department of Pathology
Maria Skłodowska-Curie Memorial
Cancer Center and Institute of Oncology
ul. Roentgena 5
02-781 Warszawa
Poland
phone: +48 22 546 27 26
e-mail: annacieckiewicz@coi.waw.pl
The author of correct diagnosis is: Maciej Znaniecki MD ,
Janusz Korczak Memorial Provincial Specialistic Hospital in Słupsk, Department of Pathomorphology, ul. Hubalczyków 1, 76-200 Słupsk
