Benignmetastasizingleiomyoma (BML) is an uncommon condition wherehistologicallybenignsmooth muscle tumors spread to locations outside the uterus(7). Few cases of BML have been documented in medicalliterature. This diseasetypically affects women in theirlate reproductive or premenopausalyears, many of whom have a history of surgicallytreatedleiomyomasthroughmyomectomy or hysterectomy. Our patient underwent 3 surgeries for recurrentuterineleiomyoma.
The mostfrequentclinical manifestations include progressive dyspneaduring exertion, pneumothorax, and chylous effusions. Conversely, the absence of systemicsymptoms or anysymptoms, coupledwith a history of uterinefibroids or prioruterinesurgery, stronglysuggests BML. In our case, No respiratory or thoracicsymptomswerereprted by the patient.
The mostcommonsite for metastasisis the lungs, accounting for 80% of cases. Otherreported sites of metastasiscan include the heart ,liver, lymphnodes, skeletal muscle and central nervous system. Zong et al (8)report in hispaper, the case of a 51 yearoldwomanwith a history of uterineleiomyomapresentendwith an osteolytic damage and spinal canal compression. Lymphnodesmetastasis are rare but not excluded as exemplified in this case. .
CT imaging of the chest and abdomen mayindicatemalignancy or infection. BML typicallyappears as well-definedlung nodules on CT scans. Bilaterallung nodules are more commonthan multiple unilaterallesions or solitary nodules. These nodules can vary in size and maycavitate, resulting in thin-walled or thick-walledcysts(9). In our case,too, the chest CT showed diffuse bilateralpulmonary nodules.
Ultimately, a histologicaldiagnosisisnecessary to establish the diagnosis of BML. This couldinvolvelungbiopsy and lesionresection.Therefore,immunohistochemistryis the key to accuratediagnosis. The typicalimmunophenotypes of PBML cellsinclude SMA (+), desmin (+), ER (+), and PR (+), whereas Ki-67 index isgenerallylessthan 1%(10).In this case, immunohistochemistryshowedpositivity for smooth muscle actin, ER, PR, and ki67 index was 5%.
The exact origin of BML remainsunclear and subject to controversy and varioushypotheses have been proposed. The mostwidelyacceptedtheorysuggestshematogenous spread of a monoclonal elementwithin a benignsmooth muscle tumor. It isalsosuggestedthattheremaybe a derivation of an independentsmooth muscle proliferation or potentialderivation of a low-grade leiomyosarcoma(11).In this report, Wu et al. (12)usedparallelsequencing and genome-wide copy number to detectlung and uterineleiomyoma in synchronized tissue samples. It wasfoundthat the somatic mutation and copy number aberrations were the same inchromosomalabnormalitiespairedpulmonary and uterineleiomyoma. A potentiallydeleterioussomaticheterozygous mutation in the bonemorphogeneticprotein 8B genemayplay a facilitatoryrole in the metastasis of BML(13). It hasalso been detectedin 25% of thesetumors, such as balanced translocation, trisomy 12, or 6p rearrangement of 6p(14). Wewereunable to complete a geneticstudy for our patient.
Due to the rarity of thisdisease, no standardizedtreatment for BML has been proposed. Various articles published in the literaturesuggestthat the treatment can includeregular and vigilant observation ,surgicalresectionwithoophorectomy( surgical castration),medical castration using aromatase inhibitors, estrogenreceptorblockers (such as tamoxifen and raloxifene) , GnRH agonists ,progesteronetherapy, tyrosine kinase inhibitors (such as imatinib), (15,16).Our patient benefitedfromchemical castration with GnRH analogues withtumorstabilityafter 8 years follow-up.
In conclusion, the prognosis for BML patients isgenerally favorable, and pulmonarylesions are typicallydiscoveredseveralyearsafterhysterectomy or myomectomy, showing slow growth. Although rare, simultaneousmetastases to retroperitoneallymphnodes post-surgeryrequireprolonged surveillance for earlydetection of recurrence or distant metastases.
Givenlimitedtherapeutic options, thereis a need to explore and consider new drugs or therapeuticstrategies. Long-term follow-up isalsorecommended to betterunderstandtheir implications in clinical practice.
