Metastatic histiocytic sarcoma of breast

A 35-year-old female patient presented to our hospital with abdominal pain, progressively increasing abdominal distension and loss of appetite for a period of 25 days. There was no associated loss of weight.

Contrast-enhanced computed tomography (CECT) of the abdomen revealed findings consistent with peritoneal carcinomatosis along with neoplastic involvement of the adrenals, perinephric, suprarenal and infrarenal lymph nodes. The lesions showed homogeneous enhancement with contrast (Figures 1a, 1b, 1c, 1f and 1g). Periureteric soft tissue mass was noted on the left side with mild hydronephrosis (Figure 1c]. Several jejunal loops showed diffuse wall thickening with no evidence of obstruction (Figure 1d). Subcutaneous abdominal wall deposits were also noted (Figure 1d). These findings are consistent with disseminated intra-abdominal neoplastic disease.

Homogeneously enhancing lesions were seen in both breasts (Figure 1h). The breast lesions were further evaluated with mammography and ultrasound. Mammography revealed bilateral oval, partially obscured, isodense masses with no calcifications. There were no associated features of architectural distortion/skin thickening/skin retraction/nipple retraction (Figures 2a and 2b).

Ultrasound of the right breast mass revealed an oval hypoechoic lesion with circumscribed margins, parallel orientation and no internal vascularity (Figure 3a). Ultrasound of the left breast mass revealed an irregular lesion with indistinct margins and heterogeneous echotexture. The lesion showed internal vascularity (Figure 3b). The right breast lesion was assigned BIRADS 3, and the left breast lesion BIRADS 4b.

Ultrasound-guided biopsy of the adrenal and breast lesions were done. The right breast lesion was biopsied in view of disease staging and turned out to be a benign fibroadenoma. Histopathology of the left breast lesion and adrenal lesion turned out to be small round blue cell tumours (Figure 4). Immunohistochemical analysis revealed features favouring a diagnosis of histiocytic sarcoma with positivity for CD163, CD68, CD43 and CD4 (Figures 5a, 5b, 5c and 5d). A diagnosis of metastatic histiocytic sarcoma of the breast was made.

Background

Histiocytic sarcoma is an extremely rare disease, accounting for less than 1% of all haematologic malignancies [1]. The clinical presentation is varied and depends on the organ systems involved [1]. The most commonly involved organs include skin, soft tissue, and the gastrointestinal tract [2]. To the best of our knowledge, there are no reported cases of metastasis of histiocytic sarcoma to the breast. However, there has been a case report of histiocytic sarcoma of the axilla [5].

Imaging Perspective

Breast metastases are uncommon [7]. They pose a clinical challenge owing to the fact that the treatment of primary breast malignancies and breast metastases are different [7].

Metastases can be either lymphatic or haematogenous. Haematogenous metastases are more commonly located in the upper outer quadrant and superficially in subcutaneous tissue or adjacent to the normal breast parenchyma because of the rich blood supply [6].

In contrast, primary breast carcinomas are usually deep-seated. Despite the superficial location, there is no associated skin or nipple retraction [7].

On mammography, metastatic breast lesions can present as well-circumscribed or ill-circumscribed masses or as focal asymmetries. Some can be completely occult [7]. Microcalcifications are generally not seen. However, a few cases with microcalcifications have been reported in ovarian, thyroid and a few mucin-producing gastrointestinal tract malignancies [6,8–10].

Most common ultrasound features include well-circumscribed, single or multiple hypoechoic masses without spiculations, calcifications or architectural distortions. Posterior acoustic shadowing seen in primary breast carcinoma is also generally absent in metastatic lesions [7]. Similar findings were noted in our case, with the lesion being fairly superficial with no skin retraction/microcalcifications/spiculations/architectural distortion (Figures 2a, 2b and 3b).

The most common mammographic finding of breast sarcoma is a single oval hyperdense mass with indistinct or circumscribed margins and no calcifications [3]. Spiculated margins are rarely seen [3]. The presence of indistinct margins and the absence of calcifications are the most valuable mammographic features [3]. On sonography, a sarcoma of the breast typically presents as an oval mass, with indistinct margins, a hypoechoic or complex echotexture, posterior acoustic shadowing, internal vascularisation (on Doppler assessment), and no calcifications [3]. It is uncommon to see skin thickening or suspicious axillary lymph nodes [3]. Our case had similar findings with indistinct margins, heterogeneous echotexture and no calcifications. No significant axillary lymphadenopathy was noted (Figures 2a, 2b and 3b).

Overall, radiological findings alone are inconclusive, with the imaging features often mimicking those of primary breast malignancies. Sometimes, lesions can be well defined, in which case it becomes difficult to differentiate them from benign tumours like fibroadenomas [11].

Hence, it is essential to biopsy these lesions before deciding the treatment course. Immunohistochemical analysis becomes necessary in many cases to arrive at a final diagnosis [7].

Outcome

Due to the rarity and overlapping presenting features, histiocytic sarcoma is often a challenging diagnosis [1]. Because of the rarity of the disease and lack of large clinical trials, there is no standard treatment regimen. The stage of disease usually determines the treatment: surgery, chemotherapy, and/or radiotherapy [4]. Because of the extensive spread of the disease, our patient is on palliative chemotherapy and has shown partial response to treatment.

Take Home Message

Metastasis to the breast is rare; metastasis of sarcoma to the breast is even rarer. In the setting of extramammary malignancy and breast lesions, it is important to consider the possibility of metastasis. Differentiating these lesions from primary breast malignancies is essential because the treatment options are significantly different. The imaging findings of metastatic breast lesions can be quite variable and are often inconclusive. Histopathology followed by immunohistochemistry is essential for diagnosis.

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