Unilateral axillary node calcification is a rare finding on mammography and bilateral axillary node calcification is even more uncommon. During the literature review, we found a scarcity of cases with bilateral axillary node microcalcifications; and they are generally from ovarian cancer or  related to chrysotherapy (gold therapy) for rheumatoid arthritis. In fact, presence of intranodal microcalcifications may be more concerning compared to axillary lymphadenopathy.  Mammary and extra-mammary cancers need to be considered in the differentials for this finding. For this reason, the reporting radiologist must be familiar with the possible causes and guide further steps, including biopsy when needed to rule out occult cancer. Proper understanding of this condition can help to avoid unnecessary biopsies in some cases.  Here we report a rare case of bilateral axillary node microcalcifications without any known cause and revisit the etiologies and workflow to evaluate the rare finding.

A 48-year woman was found to have bilateral axillary node microcalcifications on screening mammogram (Figure 1).

Figure1: Screening mammogram in bilateral MLO projections show several fine amorphous microcalcifications (white arrows) in bilateral axillary nodes.

The microcalcifications were new compared to prior study and showed fine and amorphous morphology and hence were deemed suspicious. Her breast findings were otherwise unremarkable on mammogram and ultrasound. The patient had no history of lymphoma, gold therapy, prior granulomatous disease or trauma. On clinical examinations, no tattoos were noted in the upper part of her body. The possibility of occult breast primary was less likely due to bilateral involvement and hence an MRI scan was not offered as part of the investigation. As the cause of bilateral nodal microcalcifications was unknown, ultrasound guided core biopsy was performed to rule out the possibility of extra-mammary cancer. X-ray of the biopsy specimen confirmed the retrieval of adequate microcalcifications. (Figure 2).

Figure.2: Xray of the specimen radiograph from axillary node biopsy shows adequate retrieval of microcalcifications within the cores (white arrows).

The histology was reported as scattered microscopic round calcifications surrounded by a granulomatous reaction within the nodal parenchyma. The granulomatous reaction comprised of foreign body giant cells and aggregates of epithelioid histiocytes. The rest of the lymph node showed scattered reactive lymphoid follicles and paracortical hyperplasia. (Figure 3).

Figure 3: Fragmented calcifications surrounded by aggregates of epithelioid histiocytes and multinucleated giant cells that form a granuloma.

Special stains performed for acid-fast bacilli and fungal stains were negative.  Generally, the microcalcifications related to granulomatous disease are large and coarse while the microcalcifications seen in our case were fine and amorphous. The pathology was deemed concordant and hence she was discharged to normal screening program, being asymptomatic.  

The presence of microcalcifications in axillary lymph nodes warrants further investigation as the causes include a range of benign as well as malignant etiologies [1]. Benign conditions causing axillary node calcifications,  like tuberculosis, sarcoidosis, histoplasmosis and prior Bacillus Calmette- Guerin (BCG) vaccine, are well reported [2]. The calcifications in these conditions are generally coarse and large, especially in sarcoidosis. Axillary nodal calcifications secondary to upper body tattoos have been well reported over last two decades. Deposition of the tattoo ink within the nodes mimics microcalcifications, as the colour pigments are generally mixed with metals like titanium, aluminium, and iron during inking. Ipsilateral nodes are involved and hence it may be a unilateral or bilateral finding depending on the site of tattoo. Long term chrysotherapy, i.e. oral or intramuscular gold injection therapy, has been used for decades in the treatment of rheumatoid arthritis. The gold may accumulate in lymph nodes and simulate microcalcifications. Gold deposits may persist within the nodes for as long as twenty years after the cessation of the chrysotherapy [3]. The most common malignant etiology includes metastatic breast cancer and hence a work up to look for an occult breast primary is of paramount importance. Metastatic axillary nodes with microcalcifications from breast cancer- either occult or diagnosed on mammogram- are well known [4]. In these cases, the microcalcifications are likely to be unilateral and may show pleomorphic or suspicious morphology on the mammogram. If conventional imaging is negative for primary breast cancer, then a breast MRI with IV contrast may be the next choice of investigation in these cases to look for an occult primary. The non-breast malignancies that may present with axillary node calcifications include mucin-producing malignancies like papillary serous adenocarcinoma of ovary, scirrhous colonic adenocarcinoma and papillary thyroid cancer. Amorphous peripheral microcalcifications are generally reported in ovarian metastatic cause [5]. Treated lymphoma– post radiotherapy or chemotherapy can cause calcifications in lymph nodes which in turn represent good clinical response, though axillary nodal involvement is rarely reported. One other rare cause of axillary node calcifications is fat necrosis [6], hence the need to look for a history of trauma to the breast or axilla. To conclude, axillary nodal microcalcifications, though uncommon, is a finding that one may encounter in a busy clinical practice. The etiology may range from multiple benign to malignant causes. In some cases, differentiation between benign and malignant etiology may not be apparent and histology may be needed to rule out sinister etiology. However, careful history, clinical examination along with imaging, may help to narrow down the differentials and avoid some biopsies if benign etiology could be ascertained confidently to this finding.

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