Extraskeletal chondromas are rare benign neoplasms comprising mature hyaline cartilage. A distinctive feature of these tumors is that they develop in soft tissues away from bone and cartilage. Extraskeletal chondromas account for 1.5% of benign soft tissue tumors. They occur predominantly at 30-60, in males, and in the hand or foot. In only 4% of cases, the tumor is located not on the extremities. Patients predominantly complain of increased mass, rarely on pain or a pulling sensation. The literature on the chondromas of the anterior abdominal wall is scarce. We present a rare case of a large extraskeletal left inguinal chondroma in a 71-year-old patient. The mass was over 6 cm large, and this is the only case of inguinal chondroma described in the literature. The mass was resected with surrounding tissues (a surgical margin of 1 cm) under combined endotracheal anesthesia and the histology confirmed the tumor to be a chondroma.

chondroma, extraskeletal inguinal chondroma, sarcoma

Benign neoplasms of cartilage are rare. They mimic malignant neoplasms, particularly chondrosarcomas, and therefore require timely diagnosis and often surgical intervention.^[1] In rare cases, cartilage neoplasms are located distantly from the joints and bones. A variant is an extraskeletal chondroma.

Extraskeletal chondromas are rare benign neoplasms comprising mature hyaline cartilage. A distinctive feature of the tumors is that they develop in soft tissues distantly from bone and cartilage. Cartilaginous tumors in soft tissues have been mentioned by Paget in 1870; however, the first detailed case description of an ossifying chondroma of the soft skullcap was described in 1883.^{[2, 3]}

Extraskeletal chondromas account for 1.5% of benign soft tissue tumors. The literature describes only a few cases of extraskeletal chondromas, primarily in the upper and lower extremities. Chondromas outside the extremities account for only 4% of the cases.^{[1, 4-6]}

Here we present a description of a unique case of extraskeletal left inguinal chondroma in an elderly man.

A 71-year-old male patient presented with complaints of a mass in the left inguinal region. He first noticed the mass five years ago and asked for a consultation because it was increasing. We performed biopsy under ultrasound control (February 18, 2020). Histology showed soft tissue tumor with areas of necrosis, possibly extraskeletal chondroma. After biopsy, the patient noted that the tumor increased by 1 cm.

Immunohistochemical report dated February 25, 2020 confirmed tumor immunophenotype close to chondroma, tumor cells expressing S100, reacting with actin; total cytokeratin was negative. A follow-up examination revealed sigmoid diverticulosis without signs of diverticulitis, kidney sinus cyst, or liver calcification. Other investigations and laboratory data were normal. Abdominal CT scan showed a calcified subcutaneous mass in the left inguinal area (from 45.1 mm to 61.1 mm) not invading the surrounding structures, parapelvic cyst, and focal bone osteosclerosis (Fig. 1) . There were no laboratory abnormalities (normal blood count; normal metabolic panel with creatinine and urea; parathyroid hormone and vitamin D level were investigated to rule out hyperparathyroidism and hypervitaminosis D; calcium, phosphate, total proteins, and albumin were within reference level).

The mass was resected with the surrounding tissues (1-cm surgical margin) under combined endotracheal anesthesia (Fig. 2) . We found no invasive tumor growth in the surrounding tissues. Histology showed a skin flap with a solid tumor in the dermis and cellular tissue (Fig. 3) . Neoplastic tissue contained hyaline cartilage lobules with irregular cellularity because of areas of myxomatosis. Chondrocytes are monomorphic, without atypia. No mitotic activity is noted. Inclusions are found of calcifications and trabeculae of bone. Immunohistochemistry found positive reaction with anti-S100, negative reaction with PCK AE1/AE3 antibodies, calponin, and p63 (the reactions with actin and total cytokeratin were negative).

Figure 1.

A. Abdominal CT scan, axial section (arrow indicates mass); B. Abdominal CT scan, sagittal section (arrow indicates mass).

Figure 2.

Gross view of the tumor. A. Frontal view; B. Lateral view.

Figure 3.

Morphology. A. Gross view of the tumor; B, C, D. Tumor histology (×100); E, F. Tumor immunohistochemistry (anti-S100, ×100).

The postoperative period was uncomplicated, and the patient was discharged on the third day after surgery. There were no signs of recurrence over a 3-year period.

Extraskeletal chondromas occur predominantly at 30-60 years, more commonly in males (61%), predominantly in the hand (64%–72%) or foot (20%–24%). In only 4% of the cases, the tumor is not located on the extremities. Patients predominantly complain of increased mass, rarely on pain or a pulling sensation. The tumors almost always have a clear contour, lobular structure, and size of 1-2 cm. Histologically, they are usually represented by hyaline cartilage with areas of calcification, less often by giant cells with chondroblast activity. In 17.86% of cases, tumor may have recurrence within the next 5-6 years.^{[1, 4-6]} Calcifications are usually ring-shaped or focal in areas of hyaline cartilage.‌^[7] Extraskeletal chondromas account for only 1.5% of all benign soft tissue tumors.^{[1, 4-6]} Only one case is described with an anterior abdominal wall tumor in a child.^[4] Typically, extraskeletal chondromas are treated by marginal resection with preservation of surrounding structures and do not require extended surgical intervention.^[6] However, in large masses reconstruction may be required.^[8]

The differential diagnosis should primarily include skin and soft tissue cancers as these conditions can be life-threatening. Other conditions include glomus tumor, eccrine poroma, epidermal cyst, osteoma cutis, and calcinosis cutis.^{[9, 10]} Calcinosis cutis may be caused by a number of conditions such as trauma, inflammation, varicose veins, infections, connective tissue disease, hyperphosphatemia, and hypercalcemia.^[11] Connective tissue disease that are associated with calcinosis cutis are systemic sclerosis, dermatomyositis and systemic lupus erythematosus. Therefore, patients should be carefully evaluated if they present any symptoms of these conditions.^[12] It can also be seen in primary and secondary hyperparathyroidism or other conditions associated with calcium metabolism.^{[13, 14]} Core-needle biopsy is valid and favorable method to differentiate a benign tumor from a malignant mass. However, the sensitivity and specificity of incisional biopsy is higher than that of core-needle biopsy (88.9% vs. 66.7%) for differential diagnosis of sarcomas.^[15] Taking into account the rarity of this tumor, surgical incision remains the main diagnostic and treatment strategy. Cancers should be ruled out before surgery to understand the necessity of excision or lymph node dissection. Auto-immune and metabolic conditions are ruled out in order to avoid unnecessary surgery. A list of diagnostic modalities is presented in Table 1.

The etiology of extraskeletal chondromas is controversial. One opinion is that the tumor develops from residual fetal tissue in areas of primordial fetal cartilage. Another opinion is that the metaplasia of mesenchymal pluripotent cells forms cartilage.^[6] There are no documented cases of malignant tumor transformation.^{[1, 2]}

The histological examination usually reveals lobules of mature or immature cells (chondrocytes or chondroblasts), hyaline cartilage with variable degrees of cellularity.^[16] Immunohistochemistry is an important part of the diagnostic process, since conventional staining rarely allows chondromas to be distinguished from malignant neoplasms. Various markers are currently used, including S100, vimentin, EMA, and CK but the tissue is negative for epithelium and myoepithelial cell markers.^[17] The staining options remain open and recently an alternative marker, D2-40, has been proposed and showed a high diagnostic accuracy.^[18]

The case presented has several features. The patient was 71 years old, whereas the tumor is most commonly found in the 30-60 age range. The mass was significantly larger (over 6 cm) than similar ones. This is the only case of inguinal chondroma described in the literature. During the following 5-6 years, some tumors may recur in the same location. Therefore, the patient should be carefully monitored.

The skin and subcutaneous fat masses are common. In extremely rare cases, they may present as chondromas because of the atypical tumor location distant from bone and cartilage. The preoperative examination is needed to exclude the malignancy.

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The authors have declared that no competing interests exist.